Should I replace my OEM thermostat?

I just got my 180 hi-flow thermostat from ZZP and put it in. I took the car out and noticed a nice difference in temp over the stock stat. It was very easy to do and took only 5 minutes. I want to know what to do next, any ideas?

colder plugs would be my next mod....

Get some AutoLite 104 plugs. Is your intake a FWI or is the filter sitting in your engine bay? If you don't have a FWI, you should do it. The write up is here - https://rivperformance.editboard.com/series-ii-engine-transmission-f4/write-up-building-a-custom-4-fwi-t107.htm?highlight=custom+4

X3 on cooler plugs, AL104's are a good choice.

I'd also look into a 3" downpipe, Hogan Performance makes a good one, either by itself, or with their hi-flow Magnaflow cat.

Thanks for the advice, 104's it is for the next move followed by ported exaust manifolds and that Hogan 3" downpipe.

These are just to prep the car for a ported blower with a 3.4 pully, ported lower manifold, PCM reflash to get rid of that pesky 110mph speed limit and Stage 3 heads.

I so love my Riviera!!!!!!!

May as well skip the ported manifolds and buy headers instead.

Might want to look into an HP Tuners, considering the degree of modding you seem to be planning. At a minimum get a scan tool to monitor KR, before getting too far into making changes.

YES...
Definently scan before gettin to far...
I think I'm going to skip the scanner and just get a tuner thats got scan/record capabilties. Wont be long and im gunna be buggin the hell out of you guys for tuning help

captshiner wrote:

Get some AutoLite 104 plugs. Is your intake a FWI or is the filter sitting in your engine bay? If you don't have a FWI, you should do it. The write up is here - https://rivperformance.editboard.com/series-ii-engine-transmission-f4/write-up-building-a-custom-4-fwi-t107.htm?highlight=custom+4

I did a slick mod I read about on this site. I cut a larger hole in the bottom of my stock gutted airbox. Then cut a matching hole in the fenderwell sheet metal.
I get the advantage of a CAI/FWI with a stock look. You can hear the supercharger really good now and feel more pick-up.

I also enlarged that hole in the bottom, but not a whole lot. When I put my gutted box back on next spring, I'll be looking into opening it up some more.

The lower temp thermostat is something that everyone should do. Especially anyone who is overly anal about their temp gauge like me. Owning Jeeps and Cadillacs and a Buick that blew a head gasket and didn't have a temp gauge, I am very anal about my cooling systems now. I <3 my 3.8 and wish my fiance would drive it

Here's an interesting tidbit for us all to kibbitz about...

This MotoRad stat is sold under Murray and other store brands. I should have thought that all stats would be wide open when really hot, and the little lock-tabs that they added to their design would be superfluous... I'd never really heard of a "regular" overheat causing the heat motor to fail and close the stat, as the show in their video.

http://www.motoradusa.com/products/failsafethermo/index.html

That is the thermostat I bought and put in the last time I flushed the cooling system. (Motorad Fail-Safe)
They cost about 3 times more than a "Regular" thermostat but I figured it was worth it. Just in case.

I mentioned in another thread that I've put a non-drilled 195* SuperStat in for the winter, but I forgot to post back here 2 things I learned, that we've discussed before...

First, I didn't notice this part of the advertising before, but it does appear that the thicker spring, 50% larger heat motor, and "patented V-notch" in the SuperStat do reduce the delay, cold-shock and 'bouncing' of temperature when the stat first opens. Unlike my original stat, the temperature-rise slows down in the mid-180's, and then gradually makes its way to 195... On the other hand, it seems to spend more time above its design temperature after it's warmed up than my drilled 180.

Second, I've been paying more attention to the cold starts, and the engine doesn't heat up any faster with this stat than with the drilled stat...

So, I can stay with my Un-Drilled 180* Stat and not worry about the cold winters and thermal shock.?

Rickw wrote:

So, I can stay with my Un-Drilled 180* Stat and not worry about the cold winters and thermal shock.?

Can't say as to the shock with your fancy-ass stat...

But I would say that you can drill 1 or 2 1/16" holes and not worry about the cold winter warmup.

Recently I've noticed my 5+ year-old 180º thermostat unit ($5 AutoZone) has become stuck open. There were no serious warning signs of this, in fact during the summer and fall months I didn't notice it at all, as coolant temps were in the normal 175-180º range. As the weather turned colder, I can see the engine warms up only to about 160ºF and stays there. Before, the normally functioning unit would warm up to 185º, then fall slightly as it opened, about 5 mins into the warm-up cycle.

So now I'm in the market for a new 180º unit. Since t-stat prices max out at about $20, and most around $10, I thought I'd do some research and install the best I can find. Hopefully you guys can help steer me in the right direction. Honestly, I am perfectly happy with how the older unit performed, but as with any part replaced on the car, I want to make it an upgrade if possible. I'm noticing the balanced t-stat designs seem to indicate better performance, and haven't found any quality issues.

Here are a few models I've found that fit the Riviera:

• AC DELCO 12T4D OE (Alt 180º) 12-month/12,000-Mile Limited Warranty $6.01 (Amazon)


• STANT 431-13008 180º Stainless Steel, ELAC heat motor $2.95 (Summit)


• STANT 431-13358 180º Stainless Steel, ELAC heat motor $4.95 (Summit)


• STANT 431-13848 Regular Stainless Steel 180º (1 23/32" x 13/16" x 25/32") $4.95 (Summit)


• STANT 431-35848 Stainless steel 180º $5.39 (Amazon)


• STANT 431-45848 Premium, V-notch, 180º Superstat (1 23/32" x 29/32" x 29/32") $5.95 (Summit)


• GATES 33428 Regular 180º Reverse Poppet (1 23/32" x 13/16" x 25/32") $7.24 (Amazon)


• GATES 33428S Premium 180º (1 23/32" x 29/32" x 29/32") $5.19 (Amazon)


Something gives me the idea Gates and Stant are the same?

• SUMMIT Racing SUM-360180 Stainless Steel/Copper/Brass, 180º, High-Flow $7.95 (Summit)


• HYPERTECH 1018 Power Stat, 180º High-Flow, Stainless Steel $4.95 (Summit)


• HYPERTECH 1019 Power Stat, 180º High-Flow, Stainless Steel $9.95 (Summit)


• MOTORAD 239-180 Copper case 180º, Offset design, air relief $11.25 (Amazon)


• Motorad 7239-180 Failsafe (locks open) $15.47 (Amazon)


• JET Performance 10115 Powertech 180º High-Flow Stainless Steel $10.46 (Summit)


• JET Performance 10170 Powertech 180º High-Flow Stainless Steel $12.71 (Summit)


• WILSON Manifolds 557180 MotoRad Failsafe, High Flow 180º $15.75 (Summit)


• MR. GASKET 4364 Copper/Brass 180º Performance High-flow $13.95 (Summit)


• MILODON 16401 High-Flow 180º, Stainless Steel, "Balanced Sleeve" Design $13.95 (Summit)


• EMP/STEWART 301 (modified RobertShaw) "Balanced Sleeve" 180º Drilled, High-Flow, Copper/Steel $14.88 (Summit)


• EMP/STEWART 308 (modified RobertShaw) "Balanced Sleeve" 180º High-Flow, Copper/Steel $14.88 (Summit)


• FLOWKOOLER/ROBERTSHAW 330-180, 51211.51 BALANCED, High-Flow 180º, Copper/Brass $12.99 (Quadratech)


Assuming Milodon, EMP/Stwart, & Flowkooler/RobertShaw are all basically the same unit.

An odd ball 170º I found from a respected brand:

• MEZIERE Enterprises WN0070170 Standard Flow 170º, Copper/Stainless steel $16.25 (Summit)

I haven't got a clue as to which one is best, but I use the STANT 431-45848 Premium, V-notch, 180º Superstat

HAPPY NEW YEAR !!!

Over the years I have come to trust Stant and Robertshaw.

I installed a Stant 180* from napa (not sure which model #) when i first got my car 100,000miles ago. Still seems to be operating fine still.

Im not sure you would see any difference between any of them, especially since you didnt see much difference when yours was working vs stuck open.
However, from the pictures i would venture to guess some can flow better than other when open, though i dont know if even the worst one can underflow the WP and system at 15psi.

Good point. Maybe I'm looking into it too much. I may just get another Stant (I think that's what I have now), or I might try a few and compare results.

One thing that's odd: some of the units (including RobertShaw) that I listed from Summit show they work for GM 3.8L/231cid V-6, but NOT after 1986. Anyone know what changed after '86 that would exclude later years? I found a clue at the turbobuicks board:

"Good news, sort of. Yes, the Robert Shaw/ Mr Gasket 330-160 thermostat can be cut down to fit the 86/87 motor. Bad news. It may not work very well.

I spent this afternoon playing around, and ground down the lip on a old RS 330-180 stat to 1 3/4", to fit inside the manifold. It fits really well. (And is still very solid)

Here is the problem: The body diameter (part that moves) of the stat is 1 9/16". The ID of the inner step of the manifold bore is 1 11/16". The wall thickness of the manifold casting where the stat seats is 1/4". The stroke of the stat is 3/8"

So since there is only 1/16 clearance between the stat body (part that moves) and the housing bore, not a lot of flow will happen until the stat is almost fully open. 1/4" of 3/8" stroke upon the initial opening, is restricted by the casting thickness, so that leaves 1/8" of unrestricted flow when the stat is fully open, kinda defeats the purpose."

Link: http://www.turbobuicks.com/forums/buick-v6-turbo-tech/5383-robert-shaw-thermostat.html

So at this point, I am starting to wonder: A) if the RobertShaw would even fit, and B) would it operate correctly? Does anyone have experience using one in a modern 3800 V-6?

Where did you get the part number for the RobertShaw? They make thermostats for many applications. I'm sure they make one specifically for our 3800.

What happened in '86/'87? The end of the RWD 3.8 V6. The guys on turbobuicks.com are probably discussing the RWD 3.8. Not the Series I 3800, which was available in FWD form in the same era. (My mom's '86 Century 'vert had a 3800 with SPFI, pretty potent for a FWD car in it's day)

I found the RobertShaw part number at Summit Racing, which is specifically for 3800 V-6, but not listed for any after 1986. Using that number to Google search, I found the thread at TurboBuick.com, where they talk about modifying the lip to fit the GN motor.

It got pretty cold today (23ºF), so I decided to get one from AutoZone again. Their best unit was the Motorad Fail-Safe for $12.00, which is better than the Amazon price listed above. I think, based on how my current one is stuck open, I may have purchased the same one last time. Guy at the counter said they only sell 3 brands: Duralast, Motorad, and Valuecraft. He recommend against Valuecraft.

Planning to install tomorrow evening. I will verify if the old unit is a Fail-Safe or not.

Turns out the older t-stat unit was a Motorad, but not the Fail-Safe type. Surprisingly, the unit had not failed. Instead I found the rubber o-ring seal had broken away in two spots, allowing coolant to flow around the t-stat. The points of failure correspond to locations of assembly/weld points, where the valve support attaches to the flat disc:





Technically, the price of the repair was only $2.99 for the failed seal - I installed the new Fail-Safe t-stat since already I bought it. Will keep the other as back-up.